Apply procedure-syntax.md

Author: Sporarum

docs/_spec/04-basic-declarations-and-definitions.md

@@ -609,43 +609,6 @@ By contrast, the following application is well formed and yields again the resul
 sum(xs: _*)
 ```
 
-### Procedures
-
-```ebnf
-FunDcl   ::=  FunSig
-FunDef   ::=  FunSig [nl] ‘{’ Block ‘}’
-```
-
-Special syntax exists for procedures, i.e. methods that return the `Unit` value `()`.
-A _procedure declaration_ is a method declaration where the result type is omitted.
-The result type is then implicitly completed to the `Unit` type. E.g., `def ´f´(´\mathit{ps}´)` is equivalent to `def ´f´(´\mathit{ps}´): Unit`.
-
-A _procedure definition_ is a method definition where the result type and the equals sign are omitted; its defining expression must be a block.
-E.g., `def ´f´(´\mathit{ps}´) {´\mathit{stats}´}` is equivalent to `def ´f´(´\mathit{ps}´): Unit = {´\mathit{stats}´}`.
-
-###### Example
-Here is a declaration and a definition of a procedure named `write`:
-
-```scala
-trait Writer {
-  def write(str: String)
-}
-object Terminal extends Writer {
-  def write(str: String) { System.out.println(str) }
-}
-```
-
-The code above is implicitly completed to the following code:
-
-```scala
-trait Writer {
-  def write(str: String): Unit
-}
-object Terminal extends Writer {
-  def write(str: String): Unit = { System.out.println(str) }
-}
-```
-
 ### Method Return Type Inference
 
 A class member definition ´m´ that overrides some other method ´m'´ in a base class of ´C´ may leave out the return type, even if it is recursive.

docs/_spec/A?-scala-2-compatibility.md

@@ -16,4 +16,20 @@ of `Int`.
 
 When reading class files compiled with Scala 2, Scala 3 will do a best
 effort to approximate existential types with its own types. It will
-issue a warning that a precise emulation is not possible.
+issue a warning that a precise emulation is not possible.
+
+### Procedure Syntax
+
+Procedure syntax
+```scala
+def f() { ... }
+```
+has been dropped. You need to write one of the following instead:
+```scala
+def f() = { ... }
+def f(): Unit = { ... }
+```
+Scala 3 accepts the old syntax under the `-source:3.0-migration` option.
+If the `-migration` option is set, it can even rewrite old syntax to new.
+The [Scalafix](https://scalacenter.github.io/scalafix/) tool also
+can rewrite procedure syntax to make it Scala 3 compatible.